1. Field of the Invention
The present invention relates to a ring interferometer.
In certain interferometric systems, such as gyrometers, the use of a particular, so-called "minimum reciprocal" configuration enables exact cancelling of any phase shift other than those induced by non-reciprocal effects. These non-reciprocal effects are in particular the Faraday effect (colinear magneto-optic effect) and the Sagnac effect, according to which, by relativistic inertial effect, the rotation of the interferometer with respect to a Galilean reference frame destroys the symmetry of the propagation times.
Gyrometers with minimum reciprocal configuration are known. Particularly simple, this configuration comprises a splitting device, with three monomode gates, necessary to inject the incident light into the ends of a fibre optic loop constituting the sensing portion of the interferometer.
The single input-output section of the splitter constitutes a unimodal filter which ensures the perfect optical reciprocity of the system. According to one embodiment, the splitter is multifunctional: it ensures the mode filtering by polarising the light, and the modulation of the counter-rotating waves to enable the processing of the signal detected. The system furthermore comprises a light source and an optoelectronic detection device. According to a preferred embodiment of this known device, the various abovementioned elements are collected together in a single box of small size connected to the electronic monitoring device by a power supply cable and a transport cable for the information coming from the detector.
These electrical cables, even when they are well shielded, are subject to electromagnetic disturbance, which perturbs the measurements of the signals detected.